RAID card that can 'grow' the array

thewanted · 6 Aug 2010 at 08:10

Hi all,

I have a Drobo v2 with 4 x 2TB disks that is reaching maximum capacity. A part of me wants to get another Drobo and fill it up with some disks, because it'll be the easy way to resolve the problem.

However, there are 4 problems with the Drobo:

1) It is exceptionally slow. Performance varies wildly from 3MB/sec --> 22MB/sec. Don't even think of making it multi-task.
2) It is noisy.
3) It is not particularly cheap at ~£300 + disks.
4) If my PC is already on, why do I need another device?

At the moment I have a Dell Vostro 420 which serves my needs well. I believe it has space for 4 x 3.5" disks.

Are there any RAID cards that can perform a similar function to the Drobo? The ability to grow the array with the Drobo is the number 1 reason I bought it. The thought of buying a RAID card and being stuck with the array size I initially configure on it makes me want to weep.

Any suggestions or recommendations?

Thanks in advance

reygjabla · 6 Aug 2010 at 08:31

Looking for the same thing as well.

rpstewart · 6 Aug 2010 at 08:41

Most RAID cards will do online capacity expansion but generally it's not a particularly flexible approach:

1) While the array can be expanded you still need to deal with extending any partitions on the disk manually.

2) Unless your array is just a simple spanned JBOD affair any extra disks really need to be the same size as the originals or the extra space is wasted. For example adding a 2Tb drive to a 3x1Tb array will turn it into, in effect, a 4x1Tb array with the remaining space unavailable.

thewanted · 6 Aug 2010 at 08:46

rpstewart said:
Most RAID cards will do online capacity expansion but generally it's not a particularly flexible approach:

1) While the array can be expanded you still need to deal with extending any partitions on the disk manually.

2) Unless your array is just a simple spanned JBOD affair any extra disks really need to be the same size as the originals or the extra space is wasted. For example adding a 2Tb drive to a 3x1Tb array will turn it into, in effect, a 4x1Tb array with the remaining space unavailable.

Thanks for the prompt reply

So would I have to ensure that all disks are of the same capacity, expand the array and then use diskpart.exe to extend the partition to use the new extended space?

What's the risk associated with expanding the array? Is it still a fingernail-biting experience or have the RAID card vendors nailed the process down?

rpstewart · 6 Aug 2010 at 08:59

I've expanded arrays a few times and it's a straightforward process although it did take a while because it was RAID5 I was dealing with. Even happens in the background so the PC isn't tied up for hours on end.

You're shifting large amounts of data around so there's always a risk but if you take a backup before you start then you'll be fine.

thewanted · 6 Aug 2010 at 09:04

Certainly sounds like a viable option! Can you recommend any cards or is the PERC 5/6 still the de facto standard? Can't remember which slots a Vostro 420 has, but they're definitely not PCI-X.

PhillyDee · 6 Aug 2010 at 09:13

How about using Windows Home server? There is a beta of Vail out, you could have a play with it. No need for RAID cards themselves.

thewanted · 6 Aug 2010 at 09:20

PhillyDee said:
How about using Windows Home server? There is a beta of Vail out, you could have a play with it. No need for RAID cards themselves.

Would you mind expanding on that? I was under the impression that WHS just uses software JBOD and make copies of folders you specify to other disks.

PhillyDee · 6 Aug 2010 at 09:26

It does, to add another disk you just power down, plug in disk and then through its admin console just add to pool. You can add USB to the pool as well as internal disks. If a disc fails, then disconnect it, plug in another and you are good to go. No rebuilding, no faffing about with RAID. It just works.

I have everything on mine duplicated. 5x1Tb drives. I will be upgrading to 2TB drives, in which case I will remove one from the pool, disconnect it, connect new drive and add back to the pool. I get around 70-80mb/s over my Gb network. I use remote access to my files and stream video to my PS3.

Do you actually need dedicated raid?

thewanted · 6 Aug 2010 at 09:41

I don't need RAID but from what I can gather, if I run WHS I'd have no redundancy unless I mirror the data.

At least with a RAID card running a RAID5 array I would only lose one disk to parity and all my data would be 'secure'. Surely I'd be worse off for disk space going with WHS?

lopkinfop · 6 Aug 2010 at 12:20

how would you feel about linux? you can have ZFS on ubuntu, it would be worth reading up on

thewanted · 6 Aug 2010 at 12:28

lopkinfop said:
how would you feel about linux? you can have ZFS on ubuntu, it would be worth reading up on

Was just speaking to my friend about possibly using linux

Thanks for the heads up!

The Highpoint RocketRAID 2680 RAID card looks like a very viable option, although it means getting rid of the Vostro 420 and investing in a case with 8 drive slots. Means a whole new PC + RAID card = £££.

If only the DroboPro wasn't £900

SMN · 6 Aug 2010 at 12:50

Cant you just do this at FS level using ZFS for example? Dynamic storage pool expansion etc.

thewanted · 6 Aug 2010 at 13:00

What happens with ZFS if one disk dies? Is it similar to RAID5?

Zarf · 6 Aug 2010 at 13:59

FreeNAS/ Openfiler would work fine.

Personally I'm using a Perc5 on Windows Server 2003 and have no complaints. I've expanded from an initial 3 1TB drives in RAID5 all the way to 8 1TB drives over time. Performance is great (> 400 MB/s reads/writes on the server itself, and I get 100MB/s transfer over gigabit LAN)
Adding extra drives is easy, but I don't have an easy path to 2TB disks now that i've used all 8 bays.

My next NAS, in a year or so, Is currently planned to be an Opensolaris/Nexenta based ZFS system. I'll probably have it hosting my VM's too.

thewanted · 6 Aug 2010 at 14:41

Zarf said:
FreeNAS/ Openfiler would work fine.

Personally I'm using a Perc5 on Windows Server 2003 and have no complaints. I've expanded from an initial 3 1TB drives in RAID5 all the way to 8 1TB drives over time. Performance is great (> 400 MB/s reads/writes on the server itself, and I get 100MB/s transfer over gigabit LAN)
Adding extra drives is easy, but I don't have an easy path to 2TB disks now that i've used all 8 bays.

My next NAS, in a year or so, Is currently planned to be an Opensolaris/Nexenta based ZFS system. I'll probably have it hosting my VM's too.

Hadn't considered FreeNAS/OpenFiler. The reason I was leaning towards Windows 7 + RAID card is that I would still be able to use the PC for other stuff like web browsing, video, general desktop stuff etc.

Can't you replace one of your 1TB disks with a 2TB disk and let the array rebuild onto it? I guess you'd have to replace all 8 disks before you could expand the array though. Ouch.

Whichever way I do this, it feels like it's going to be expensive

Zarf · 6 Aug 2010 at 16:12

thewanted said:
Hadn't considered FreeNAS/OpenFiler. The reason I was leaning towards Windows 7 + RAID card is that I would still be able to use the PC for other stuff like web browsing, video, general desktop stuff etc.

Can't you replace one of your 1TB disks with a 2TB disk and let the array rebuild onto it? I guess you'd have to replace all 8 disks before you could expand the array though. Ouch.

Whichever way I do this, it feels like it's going to be expensive

I could replace the drives one by one, rebuilds take 3 days or so though, so I'd have to spend the best part of a month with the drives and controller under stress with no resiliency.
I'm also not 100% positive that when I add the final disk it'll realise that the array size can be increased.

rpstewart · 6 Aug 2010 at 16:20

I had a similar problem going from 8x250Gb to 8x640Gb. Easiest way is to back it all up and start again.

8x1Tb gives you 7Tb so that goes onto 4 of the 2Tb disks (as single drives). Create a 4x2Tb array to give you 6Tb, restore 6Tb or so from the single drives then expand the array using the one's you've emptied. That should give you enough space on the array to restore the contents of the remaining single drives. Finally expand the array again with the last of the drives.

thewanted · 7 Aug 2010 at 10:09

Zarf said:
I'm also not 100% positive that when I add the final disk it'll realise that the array size can be increased.

rpstewart said:
I had a similar problem going from 8x250Gb to 8x640Gb. Easiest way is to back it all up and start again.
.

Well those two statements makes me wonder if a RAID card is such a hot idea as that's the entire point why I'm thinking of getting one instead of using WHS.

I thought the point of getting an expensive card is so that it can expand the array and you wouldn't have to resort to such drastic measures as wiping the disks and starting again.

Zarf · 7 Aug 2010 at 12:52

thewanted said:
Well those two statements makes me wonder if a RAID card is such a hot idea as that's the entire point why I'm thinking of getting one instead of using WHS.

I thought the point of getting an expensive card is so that it can expand the array and you wouldn't have to resort to such drastic measures as wiping the disks and starting again.

Well, Like I said, it's fine growing the array up until you reach 8 Drives. What I could have done is moved to 3x2TB disks after I filled 5x1TB disks, copied the data over, sold the 1TB's and grown the array with another 2TB drive, but at the time 2TB drives were very expensive per GB and I certainly couldn't afford to buy three or four at once.

as I understand things, WHS uses a mirroring based system for data protection, rather than parity, so it's not very space efficient ... if you want all your data to have some protection you'll be giving up half your disk space.

ZFS is also not ideal, you can't expand a RAIDZ after creation, although you can keep adding multiple RAIDZ's to your ZPOOL. This means although you can keep expanding the ZPOOL (your filesystem space) you lose more drives to mirroring or parity (one drive for every RAIDZ that makes up your ZPOOL)

UnRAID is the easiest solution for expansion and migration to larger drives, It is effectively software RAID 4 without striping, and can handle lots of drives of different sizes so long as your parity drive is the largest. To move to larger drives you need to replace the parity drive first, but after that you the others can be added or replaced at will.
Downside is it's not very fast. There's no striping so read speeds are capped at one disk, and writes are apparently quite slow because parity is all done in software.
Another Downside is it isn't a true single seamless file system, you need to be careful with how the directories on different disks are named and organised.
More info here: http://lime-technology.com/technology/usershares
Oh, it also costs money for the versions which can handle a decent number of drives.